External code editors like Notepad++ are the best way to maintain many memoQ resources

Notepad++ is free and open source and can be obtained here. I have an old blog post on this subject from 2019 which may be worth a look. What I failed to mention in that article is the usefulness of changing style definitions.

The Style Configurator in the Settings menu lets you assign a particular style to files with certain extensions. The "XML" style is very helpful to use for maintaining memoQ MQRES resources and text files which may contain things like tag data (or where you want to have those useful green comments):

At the bottom of the Style Configurator with the XML "language" selected, I added the desired extensions mqres and txt. Individual coloring for various XML structures can be customized by selecting them in the Style column. I didn't bother; I used the default, but maybe if you are colorblind or need different styled "hints" you might want other settings.

This is a lot easier to work with than the grim view of all black text on a white background that you would see if you simply open an MQRES or TXT file in Notepad++.

Other customizations of the working environment and user interface can be made (like changing the display language to Russian, Portuguese, etc.) under Settings >Preferences and in other areas of the menu. There are many YouTube videos and articles available to familiarize you with such options if you feel they are important. The site https://notepad-plus-plus.org/ is probably one of the best places to start looking.

Notepad++ is only available for Windows operating systems. However, there are a number of good, free alternatives available on Windows, Mac and Linux platforms. Have a look at this article for descriptions and links for some of the best:

https://www.guru99.com/best-free-code-editors-windows-mac.html