You can mark your macro with CODE tags by using the [#] icon and pasting the macro between them

These are not the most elegant way, but should work

Option Explicit


Sub abc()


    UserForm1.OB_Verksamhet_Lantbruk.Visible = False


    With ThisDocument.Bookmarks
        If .Exists("Kapitel_EKP_Lantbruk1") Then GoTo OK
        If .Exists("Kapitel_EKP_Lantbruk2") Then GoTo OK
        If .Exists("Rutin_Eldning_i_det_fria") Then GoTo OK
        If .Exists("Rutin_Elinstallationer") Then GoTo OK
        If .Exists("Rutin_Gödningsmedel") Then GoTo OK
        If .Exists("Rutin_Heta_Arbeten_Lantbruk") Then GoTo OK
        If .Exists("Rutin_Hästskoning") Then GoTo OK
        If .Exists("Rutin_Högtryckstvättning") Then GoTo OK
        If .Exists("Rutin_Inomgårdsutrustning") Then GoTo OK
        If .Exists("Rutin_Insatsplan") Then GoTo OK
        If .Exists("Rutin_Lagring") Then GoTo OK
        If .Exists("Rutin_Motordrivna_fordon") Then GoTo OK
        If .Exists("Rutin_Släckutrustning") Then GoTo OK
        If .Exists("Rutin_Torkfläktar") Then GoTo OK
        If .Exists("Rutin_Uppvärmning") Then GoTo OK
        If .Exists("Rutin_Utrymning") Then GoTo OK
OK:
        UserForm1.OB_Verksamhet_Lantbruk.Visible = True
    End With
End Sub

Sub def
    Dim b As Boolean


    b = False
    With ThisDocument.Bookmarks
        b = b Or .Exists("Kapitel_EKP_Lantbruk1")
        b = b Or .Exists("Kapitel_EKP_Lantbruk2")
        b = b Or .Exists("Rutin_Eldning_i_det_fria")
        b = b Or .Exists("Rutin_Elinstallationer")
        b = b Or .Exists("Rutin_Gödningsmedel")
        b = b Or .Exists("Rutin_Heta_Arbeten_Lantbruk")
        b = b Or .Exists("Rutin_Hästskoning")
        b = b Or .Exists("Rutin_Högtryckstvättning")
        b = b Or .Exists("Rutin_Inomgårdsutrustning")
        b = b Or .Exists("Rutin_Insatsplan")
        b = b Or .Exists("Rutin_Lagring")
        b = b Or .Exists("Rutin_Motordrivna_fordon")
        b = b Or .Exists("Rutin_Släckutrustning")
        b = b Or .Exists("Rutin_Torkfläktar")
        b = b Or .Exists("Rutin_Uppvärmning")
        b = b Or .Exists("Rutin_Utrymning")
    End With
        
    UserForm1.OB_Verksamhet_Lantbruk.Visible = b
End Sub

Yes, VBA does like (usually) to have an EndIf for every If
You can put skip the End If when the whole conditional is on one line like I did

With indenting, you can see the bracketing

Sub def()
    If ThisDocument.Bookmarks.Exists("Kapitel_EKP_Lantbruk1") = False Then
        If ThisDocument.Bookmarks.Exists("Kapitel_EKP_Lantbruk2") = False Then
            If ThisDocument.Bookmarks.Exists("Rutin_Eldning_i_det_fria") = False Then
                If ThisDocument.Bookmarks.Exists("Rutin_Elinstallationer") = False Then
                    If ThisDocument.Bookmarks.Exists("Rutin_Gödningsmedel") = False Then
                        If ThisDocument.Bookmarks.Exists("Rutin_Heta_Arbeten_Lantbruk") = False Then
                            If ThisDocument.Bookmarks.Exists("Rutin_Hästskoning") = False Then
                                If ThisDocument.Bookmarks.Exists("Rutin_Högtryckstvättning") = False Then
                                    If ThisDocument.Bookmarks.Exists("Rutin_Inomgårdsutrustning") = False Then
                                        If ThisDocument.Bookmarks.Exists("Rutin_Insatsplan") = False Then
                                            If ThisDocument.Bookmarks.Exists("Rutin_Lagring") = False Then
                                                If ThisDocument.Bookmarks.Exists("Rutin_Motordrivna_fordon") = False Then
                                                    If ThisDocument.Bookmarks.Exists("Rutin_Släckutrustning") = False Then
                                                        If ThisDocument.Bookmarks.Exists("Rutin_Torkfläktar") = False Then
                                                            If ThisDocument.Bookmarks.Exists("Rutin_Uppvärmning") = False Then
                                                                If ThisDocument.Bookmarks.Exists("Rutin_Utrymning") = False Then
                                                                    UserForm1.OB_Verksamhet_Lantbruk.Visible = False
                                                                Else
                                                                    UserForm1.OB_Verksamhet_Lantbruk.Visible = True
                                                                End If
                                                            End If
                                                        End If
                                                    End If
                                                End If
                                            End If
                                        End If
                                    End If
                                End If
                            End If
                        End If
                    End If
                End If
            End If
        End If
    End If
End Sub
I'm not sure that the way you had it will do what I think you want.

If ALL .Exists = False then .Visible = False is finally executed

If ANY .Exists = True, then the If/Then goes to the End If and the .Visible = True is bypassed