This tool, as the name clearly doesn't imply, is a block inserter designed to replace the dated BTSD. It is backwards compatible with BTSD and will upgrade your ROM when using the tool. The readme has full details on benefits. A GUI is not included in this version. If you want one download it from an older version of GPS. The GUI does not support the features of the current list and has not been kept up to date. Use the GUI at your own risk.
Simple blocks, for example Mario-only, can be created with Blockreator.
there just had to be some edge case I forgot to test where routines break again, great.
I put it on my todo list so it'll be fixed whenever I stop being lazy and actually work on the update again. Thanks for reporting.
there is an interesting special-case bug i've run into while making custom shared routines for my hack. let's say you have shared routines A,B and C. Both A and B call C within their own asm files. If you then create a block that calls both A and B, GPS will throw an error when trying to insert this that says along the lines of