I think what is needed is a variable to reverse Set(varTab, "show") in order to show the fields and change the button mode.
I suggest you change the variable to Boolean, true false.
Set(varTab, false)
Insert another that changes the variable
Set(varTab, true); ViewForm (YourForm)
Then DisplayMode of the button ;
If(varTab =true, Disabled, Edit)
With that when the new button is pressed, the field would show for View mode
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