Use 'Minimal borders' mode as default everywhere even in sub-windows
I understand the suggestion to mean:
Add the option to select 'Minimal borders' as default [like the existing option to select 'No borders' as default (instead of 'Normal borders')].
I agree - it does not seem to make much sense to have the 'Minimal borders' functionality, when you currently must select the option anew everytime you open a Floating App.
It would definitely make more sense, to have the option to select 'Minimal borders' as default, and/or the option to 'Save borders' for individual windows. Neither option excludes the other, but the latter would present the better possibility for user customization.