View virtual stack of sparse time lapse data with channels synchronized

I would like to do a similar thing to what’s described in this discussion (view windows synchronized in t), but with sparse data:

That is, some wavelengths are missing planes for some time points. In this case, I would ideally like to show either the previous image in that wavelength or nothing if there isn’t a previous image. The file names contain the wavelength and time point.

When I open each wavelength as a separate stack and synchronize, the windows are of course synchronized assuming an equal number of images in each wavelength, thus they are not synchronized in t as it is encoded in the filename.

Any ideas? I know how to do this if I first convert my separate PNG images to an OME-TIFF (where I can point the IFD to previous planes), but I want a way to quickly look at the data (which is thousands of time points) as a synchronized virtual stack before committing to long-running tasks.

I could also write something like this myself, but was hoping not to reinvent the (entire) wheel.

thanks in advance!