Two things:
The Ability list on the left of the materia info window is pretty much hardcoded in the EXE in what it shows. There are only a couple materia where it's coded to show attribute names with per-level percentages, and these are the first 5 materias (as stored in game's data): MP Plus, HP Plus, Speed Plus, Magic Plus and Luck Plus. You cannot change via simple kernel editing what text is being displayed by these materias as this is hardcoded in the EXE.
The Equip effect
can be changed by editing kernel data but there's a hardcoded list of atribute sets and their stat bonuses to choose from (see
https://wiki.ffrtt.ru/index.php/FF7/Materia_data). These are always the same no matter what level the materia is. What New Threat did with the Omni Plus materia is they've modified the EXE and put in a new stat bonus list (or changed an existing one).
Now assuming you want to have Strength Plus materia that shows a per-level stat bonus for Strength the simplest way would be to change one of the 5 aformentioned materias (MP/HP/Speed/Magic/Luck Plus) to Strength Plus, adjust its attribute to be Strength and then also modify the EXE to show the correct text in the menu. Here for example I've changed Magic Plus to Strength Plus:

To achieve this I've modified the code starting from memory address 0x70b667:
70b667 = 68 38 0D 92 00 ; PUSH 920D38 - address of "Strength" text
70B694 = 6A 7F ; PUSH 127 - X coordinate of the stat bonus number
70B6AF = 6A 73 ; PUSH 115 - X coordinate of the "+" character
70B6CA = 68 97 ; PUSH 151 - X coordinate of the "%" character