Activating this trainer:
If not state otherwise below, press F1 at main menu.
Listen for 'Trainer Activated'.
Press desired hotkey. All hotkeys can be changed on the trainer.

Promo Options:
Inventory: Click Inventory Item Amount

Editor Options:
Mouse Over Unit: Max Health
Mouse Over Unit: Current Health
Mouse Over Unit: Max Tension
Mouse Over Unit: Current Tension
Mouse Over Unit: Max Avoidance
Mouse Over Unit: Current Avoidance
Mouse Over Unit: Max Ether Operator
Mouse Over Unit: Current Ether Operator
Supplies: Current Gold
Supplies: Current Medical Supplies
Inventory: Click Inventory Item Amount

Notes:
EDITOR OPTIONS

For Mouse Over Unit options, while in combat you mouse over a unit until the tip card pops up showing the current information for the unit.  Then you can edit the values and press TAB to lock it in.

For Supplies, you enter the inventory then note the values and you can change them and press TAB to lock it in.

For Inventory, click an inventory item, then note the value shown and you can edit it and press TAB to lock it in to change the amount you have.