Any tips for editing milkway considering that it's impossible to use the brush tool?
Or, as side but related question, is it possible to edit the shots one by one togheter with LRTimelapse without using the keyframe option?

It's not impossible to use the brush tool, it's just that its position cannot be animated.
But you can animate the position of radial filters and liniear filters. More than enough for any milkyway editing.
Personally, I like to do a rather subtile editing with maximum one radial filter that moves with the milky way and one linear filter for the ground. Most images / timelapses of the milkyway are way overdone. I've explained in detail on how I shoot and edit the milkyway and how it should look in my book: https://lrtimelapse.com/buy/ebook/

Tks a lot Gwegner

Hello Gunter,
I am also attempting to shoot the milkyway on a slider with a reveal at sunset and sunrise. The complexity of the shot imposes many variables. The reveals will be stationary with only the milkyway the slider portion.

I like your idea of a linear gradient for the ground image and the radial for the milky way. For the reveals at sunset and sunrise, do you have any suggestions? I am assuming (cloud cover permitting) the dynamic range would be very close and therefore not require large changes. Do you think this will work?

Larr2000

Running on an iMac (10.15.5) / Catalina
Quad-Core i7, 64 GB
Radon 580 8 GB/Radeon RX Vega 56
LRTimelapse 5.4 Build 619
Lightroom Classic 9.3 Camera Raw 12.3

Sorry, but it's really hard to give advice without knowing about the specific situation. I've explained my approach in detail in my ebook (it covers 480 pages in total) - if you read that you will basically know all about timelapse shooting and editing that I know... :-)
https://lrtimelapse.com/buy/ebook/