This app was mentioned in 7 comments, with an average of 1.86 upvotes
# Plain text / coding:
# Simpler:
# Requires Dropbox:
# Comes with encrypted cloud:
There are lots of them (See http://texteditors.org/cgi-bin/wiki.pl?AndroidEditorFamily for a list of at least some of them.)
What editor do you use on the PC? Chances are there's something similar for Android. And what sort of editingf do you do?
What I mainly use here is 920 Editor (https://play.google.com/store/apps/details?id=com.jecelyin.editor.v2&hl=en_US), an open source text editor whose Github repository is at https://github.com/jecelyin/920-text-editor-v2
I also have DroidVim https://play.google.com/store/apps/details?id=com.droidvim&hl=en_US, an Android port of Bram Moolemar's Vim editor based on Unix vi, with the Github repository at https://github.com/shiftrot/droidvim
I've also used DroidEdit (https://play.google.com/store/apps/details?id=com.aor.droidedit&hl=en_US), QuickEdit (https://play.google.com/store/apps/details?id=com.rhmsoft.edit&hl=en_US), and a few others, but don't have them installed at the moment.
My use case is text editing on a tablet, using an external keyboard, so I look for editors suited for that.
Custom syntax - no, search & replace - yes. FOSS.
https://play.google.com/store/apps/details?id=com.jecelyin.editor.v2
I haven't tried it myself, but I think this will do the trick: