Solider Maintenance is tedious.
Select the squad
Select the soldier
Select the Perks button.
Select Perks
Select BACK
Select the next soldier
Select the Perks button
Select Perks
Select BACK
Select the next soldier
Select the Perks button
Select Perks
Select BACK
over and over
After adding buttons for NEXT and PREVIOUS soldier
Select Squad
Select Soldier (the leader)
Select Perks
Pick Perks.
Hit NEXT SOLDIER
Pick Perks
Select NEXT SOLDIER
Pick Perks
Select NEXT SOLDIER
etc.
An improvement on this would be to copy the UI from Saved Equipment Sets and recycle it for Perk Sets.
A second improvement would be to copy fhe functionality from Research in War Thunder and just have a SPEND button - preferably at the Squad Selection Screen where you could AUTO spend perk points for every soldier in every Squad with one click.