Hi @szita2000 ,
According to your description, I've made a test for your reference:
1\ This is my list ‘LIST86’. ‘UserName’ and ‘folders’ are ‘Single line of text’ columns. The value of the folders column is displayed in the dropdown control.

2\ Add a dropdown control ‘Dropdown1’ and set its Items property to:
LIST86
Set the dropdown control’s Default property to:
LookUp(LIST86,UserName=User().FullName).folders
// At this time, the default value of the dropdown control will change according to the user.
For your second question:
You could use other controls instead of form control.
For example: you could use a textinput control and a button control instead of form control.
1\ Add a textinput control ‘TextInput1’
2\ Add a button control and set its onselect property to:
Patch(LIST86,Dropdown1.Selected,{folders:TextInput1.Text})
// At this point you can modify the value of the folder column of the record selected by the Dropdown control.
// The value of the folders column is the value entered by the textinput control.
3\ The result is as follows:


Best Regards,
Wearsky
If my post helps, then please consider Accept it as the solution to help others. Thanks.