I know that Easel / Carvey support milling using 2 bits, for a situation where a larger bit is used to carve out the bulk of the material and then a smaller bit is used as a final pass.
I have also a need for 2 bits, but in a somewhat different way. I would like to use one bit for making holes and another for engraving. At the moment, I do this by having a project with both types of elements, and then before carving with one of the bits, I make a copy of the project and delete all the elements intended for the ‘other’ bit.
My suggestion is to allow one to specify the bit in the same window as the one which specifies the depth of cut. It would be best if one could chose, for example, bit ‘A’, ‘B’, or ‘C’ , etc. Then at the project level, select which bit is ‘A’, ‘B’, and ‘C’, etc. Or this bit selection could be when setting up to carve. Or even a specific bit size could be selected for each element just as the depth is selected now.
When carving, only the elements sharing a given bit would be included in the tool path. After the first tool path is finished, one could mount the second bit, let Easel know, and carve those elements.