If I'm not mistaken, the most asked off-topic questions are about writing apps.
My suggestion is:
When a person tries submitting a question which includes the words "I'm working on an app" or anything similar to that, he should get a popup explaining that questions about writing or publishing apps, are off-topic.
Same should apply to anyone trying to dump a bunch of code into the question. That should easily be recognized by the system as a red flag.
Related question Adding a template question to the Ask Question box. Perhaps such changes are not possible unless it's a global change across all SE sites
Questions having the phrase I am working on app or similar need not be developer oriented. That could be the reason for asking but the question may not be off topic. For instance, in this question , if OP had said he was developing an app for that device and wanted to know the path, it wouldn't make it off topic Copy full system and data partitions of Oneplus 3T to computer or a better example How can I do development on my Android device?
OP's are expected to search for relevant tags and if their question is related to development use development and if they bother to read to read the tag wiki , they would know not to ask (too much to expect, going by experience). See Does [tag:development] mean "Asking for closure"?
I fully endorse that questions having code should raise a flag but it is related to the first bullet point and would like this to be implemented ASAP. Perhaps , moderators here could take this up
Edit: Discovered this question on Meta.SE asked years before Revisiting question templates
development tag was introduced as a booby-trap to hunt down such off-topic questions. Unfortunately "if they bother to read to read the tag wiki" is a joke, as too many questioners don't even bother reading the excerpt. So if you want to hunt for questions you can VTC, simply subscribe to that tag ;)
"Questions having the phrase I am working on app or similar need not be developer oriented" true. That's why we shouldn't block them, rather the asker will be informed that this question might be off topic. "and if they bother to read to read the tag wiki , they would know not to ask" i was using the SE app from my day one. I didn't even know that when searching for tags, you get more info about it. Chances are, people asking questions about Android phones, are using the mobile version, which also doesn't show info about tags. Therefore Development tag should show a warning before posting