Your method for memorizing is exactly how i approach the more complex tax formulas. Accrual, wealth, and CG tax formulas are intuitive once you understand the formula, as is Taxable Gift…. so memorize Taxable gift and then just add the “changes” eg tgte as you have above, then you really are only memorizing a slight modification since you should already know the taxable gift formula.
Did the same thing for the ridiculously tedious “charitable bequest”. I forgot that one, but i think it’s the bequest formula times toi + 1+r^g
Easier to memorize the “bread and butter” problems and then just tack on the changes for the heavy stuff.