Alright, here we go. It may seem convoluted a bit, so do ask any questions that you have. I will edit this post and screenshots in a day or two to make things a bit easier to follow. I also can post it as a guide in a separate thread should anyone need it.
I. What you need:
1. Okapi Applications:
https://bintray.com/okapi/Distribution/Okapi_Applications2. OmegaT (go for 5.2.0, despite the Beta indication its rock-solid):
https://omegat.org/II. Setting up the project:
0. Download translation *.txt files for MusicBee and put them wherever is convenient to you.
1. Unpack Okapi Apps somewhere convenient
2. Go into the Okapi Apps directory and launch rainbow.exe - we will use this thing to convert files back and forth.
3. Click ... near the Root 1 field and set root directory to wherever you put the localisation files.
4. Go to Languages and Encodings tab and indicate your source (en-us will do) and target (whichever one you're translating to) languages
5. In the input list 1 tab, Right Click -> Add Documents, choose the files.
6. Now click on Filter Configuration column opposite any of the files added. Here's where we set up filters to extract the text strings.
7. In the Input Document Properties window, choose Plain Text Filter from the drop-down menu, and then click the Create Button. Name the filter whatever you want.
8. In the Plain Text Filter Parameters window, choose Extract with a rule in the Extraction mode section.
9. Now you have to figure up a RegExp to extract just the text you need to translate to minimize the chances of botching anything. Here's what I come up with:
(\#\t{1,}|\#\s{2,})(\s*?\"*?\s*?\'*?\{*?\(*?\%*?\/*?\[*?\{*?\<*?\&*?\.*?\w.*|\s\t\#\s*\[*?\w.*|\s*?\%\s\w.*|\t\/\s\w.*|\t\-*?\,*?\s*?\w.*|\#\s\t{1,}\@*?\,*?\|\s*?\w.*|\@|\*\s*?\w.*|\/\s*?\w.*|\-\s*?\w.*|\#\s*\[\w.*|\,*?\s*?\w.*|\#|\|\s*\w.*|\,\s\{\w.*|\+\s*?|\^\w.*|\'*?\W*\w.*)
Not the most elegant one out there, but it works for me. You are welcome to optimize it. Be sure to test it somewhere though 'cause you might miss some strings, and you won't know it, until the app throws an exception. Source group is set to 2 by default, leave it there.
10. Make sure you set the filter for all the files.
11. In the top menu, choose Utilities -> Translation Kit Creation.
12. In the Pre-Defined Pipeline windown, choose Rainbow Translation Kit Creation and select OmegaT Project in the Package Format tab on right pane (or whatever format is preferable for the tool of your choice, e.g. PO package if you like POEdit better).
13. In the Output location tab, indicate the project name in Name of the package field.
14. Press execute to create the project in the root directory you set earlier.
15. Make sure to save the project somewhere safe.
III. Working with the project
1. Install and launch OmegaT.
2. In the top menu, Project -> Open. Locate the project you set up with Rainbow and have a good time translating it!
3. Once finished, press Ctrl+D to create translated files.
IV. Converting back
Now return to Rainbow
1. Open the project you saved earlier.
2. Don't change anything, just remove the files.
3. Add the manifest.rkm file from your OmegaT project folder
4. Now from the top menu choose Utilities -> Translation Kit Post-Processing
5. In the window that opens, click the Execute button.
6. Now you can find the translations in *.txt format in the done/ folder inside your OmegaT project folder.
V. You know the rest
1. Merge the text files into one
2. Change the extension to .lng
3. Put into MusicBee Localisation folder and test your localisation out!
Make sure to backup your project tmx and glossary files so that the translation are not lost.