I’ll rehash some old ground (already captured) in terms of feature suggestion, but maybe it has some relevance for op as well.
The feature suggestion is Extra Password for the app-unlock process
When using PIN unlock on mobile, a long PIN is not needed for security as long as there is a limit like 5 incorrect attempts before the PIN is blocked and full password is required (like how Bitwarden mobile implements it). From my simplistic view, it seems like an obvious way to maintain both high convenience and high security on mobile, but I may not understand the full security impllications or the resources to implement it
At any rate, the potential practical part for the op while we’re waiting for the feature to be evaluated, I found there are 3rd party app lock pin products that can be used instead to roughly accomplish the same thing. I discussed how I use Norton app lock in my post at the end of that thread (there are some ins and outs that I won’t repeat, I suggest read my comments if you’re interested).