I'm a big fan of projectionlabs and have recommended it to a few people. It's the best tool I've found in this niche. You've done a great job on the UI to keep it simple while being extremely powerful and I love moving milestones around and seeing how things react.
The Tax side is where things get interesting/complicated. In my case, I'll be retiring in a different country to where I'm working and so the tax for drawdowns doesn't really work
Re: moving/retiring to a different country, would it potentially help to create a milestone to model this and add Tax Consequences to that milestone? That can be used to switch your tax config to a different international preset starting in a certain year, or apply new custom brackets/config, etc.
I am not really sure the consequences of e.g. withdrawing from a US 401k while UK resident (as a US citizen). But treating the 401k as an analogous UK pension for withdrawal purposes would probably be correct enough for forecasting.