I play Shattered Pixel on my phone, and sometimes circumstances cause a mistap or similar, and with the way this game works a single bad action can mean a drastic hinderance on the run or effectively ruin large amounts of effort.
This is true for many games, and in most circumstances I can roll back to the last save and lessen the loss. While in plenty of others I can edit the save files with a shizuku-powered file manager. I had hoped that the non-google android version on github would expose the save files to shizuku, but sadly learned that was not the case. Of course, there are others where neither are an option and I just have to live with it, but I just tend to not play those games for long or that much. However, I've been playing Shattered Pixel for years. It's easily the one mobile game I have spent the most time playing. But it can really kill my desire to play for long periods of time when something happens to kill a run I was really enjoying and spent a good amount of time on and there is no way to "undo" any amount of the loss.
For me, it would be an absolute game-changer if there was some way to allow manual save/loading or access to the save files. If it means by an opt-out of online leaderboards or whatever I'm okay with that. (I'm not sure what there is for SPD, I really don't know because I only care about offline regular play.) You can mark my game a "filthy gross evil stinky dirty cheater" or something, I don't care. Personally, I don't consider it "cheating" to recoup from a mishap outside of their control in an offline singler-player game.
Is the threat of some sort of bad-actor that high that save/reload or save file access can't be considered? What exactly would be on the line by allowing "cheating"?
I have to imagine there would be a sizable enough group of people interested in manual save/load or save file access considering there are save editor tools out there, like spud. It would also allow easier transfer of game progression like this request mentions.
Is manual save/reload something that would interest others that you know of? At least, enough to get 00-Evan to consider some sort of option? Can we work out some sort of option that 00-Evan would consider?

As someone with ADHD that gets distracted easily and makes lots of silly mistakes, I feel your pain. It's a single player game, cheat if it makes you happy.
On Windows you can save scum (back up the save files when you want, I did it every new floor when I was learning, then copy them back to the save folder on death).
On Android, you can install ElectroCheckers SHPD Toolkit from Github which doesn't allow save backup, but gives you lots of information about the run so you have a large advantage (what all the potions and scrolls are, what levels have secrets, what fixed items will drop, what the quests will be etc).
Once you have won once you can use the seed to re-try promising runs to try different tactics/builds.
All that said, I'm against a built in save/load mechanic. It would take away the key component that makes this a roguelike. Permadeath is kind of the whole point. When I die to stupidity, i laugh and go to sleep like I should have three hours ago.