Thanks a lot. It's great that you could figure it out. I'll try to find out what's going on with the key exported by 1Password. 

Can you please send me an example private and public key file including a passphrase so I can try to reproduce the problem here? 

You can send it to support@textasticapp.com

Or tell me how exactly you created the private key file.

Did you enter the passphrase in the password field?

Hello,

Step 2 is not needed. You can open the preview while the JS file is active and enter the path of the HTML file that references the JS file in the address bar of the preview window. Textastic will remember the path you entered.

This is explained in the manual at https://www.textasticapp.com/v9/manual/viewing_editing_files/web_preview.html:

By default, tapping on the web preview button will show a preview of the file currently open in the editor. 

If you want to view another local file, you can enter a different local file path in the address bar.

Textastic will remember the local path and remote URL you enter for each file and restore it the next time you open the web preview for that file.To reset the local path or remote URL, tap on the address bar, clear the contents of the address bar using the gray X button and press Go or Return on the keyboard.

Thanks for letting me know about this issue. I'll try to reproduce it.

Hello,

unfortunately I'm not familiar with Tailscale. Is there an easy way for me to setup such an SSH environment for testing purposes?

Currently Textastic supports password, password interactive and public key authentication. Multi-factor authentication or authentication with an http link as you are describing is not yet supported, but I'm willing to look into it.

Thanks for your interest in Textastic for macOS. The macOS version and the iOS/iPadOS version of Textastic are two separate apps for two different platforms with different feature sets (the macOS version doesn't have remote connection support), so it would require two purchases if you want both.

There is a trial version version of Textastic for Mac at https://www.textasticapp.com/mac.html. The download link is below the big green button.

Yes, you can already open files from OneDrive using the "Open..." command in Textastic:

https://www.textasticapp.com/v10/manual/integration_other_apps/external_files_folders.html

Hello,

thanks for your bug report. I can reproduce the issue. I'll try to find out what's going on.

Workaround: Search for [ A-z]+ instead of [ A-z].