yes, I started this some time ago, but never did any further developement. possibilities for building the user interface were ... unsatisfying. Still I am thinking, it would be a good idea to have a native Pd wavetable editor.
I was thinking of something useful, but specifically "nice" (like pd itself). What you managed to do works quite nice, but it is really necessary to code a lot to do something so simple like a button which stays down. Since pd allows you to do everything, why not also this tool? My priority would be precision but not (too much) user-friendlyness.
By the way, I wanted to use it exactly for (wavetable) editing, but for example also as a channel-splitter: I have now and then several multichannel files (usually 4) which I have to split and edit (basically cut the corners) - but all channels must be coordinate on the sample level - and later mix it as I want (on a mono or stereo file, with one or more channels).
That doesn't sound difficult to do, the only problem might be the limit of 4e06 samples for each array. Is there a way to change this limit?