One of the most persistently useful tool I've made for dealing with strange displays is a grid generator. Making PNG screenshots is kinda challenging so I ended up using a library to recreate the DOM within a <canvas> object, then capture that as an image. It was fun to play around with Svelte. https://dgtlworkshop.github.io/dgtlGridGenerator/
I need to deal with the text scaling when viewed in person as the scaling can get kinda gross. I should really just render everything within a <canvas>, but Svelte's DOM control is pretty fun.