hello southsidejakey,
From what I learned by reading “what’s new” UE 5 compiles shaders on demand, that is, it doesn’t compile them all at once.
For example if you create a 3rd person shooter from project template it will compile shaders used by scalling options for that template, later if you create another project from another template it will compile specific shaders not compiled before, and so on depending on template.
Also if you switch to sculpting it will compile additional shaders that were not compiled before.
I can confirm this from my own experience, and the longer I use UE less and less shaders get compiled over the time.
As I continue creating new projects (for learning purposes) less and less shaders get compiled.
There is also another concept when it comes to shader compiling as follows:
If you set your project scalability settings to ex. “Medium” shaders will be compiled for that scalling, then each time you create a new project with “medium” scalling compiled shaders will be resused, HOWEVER!, if you change the scalling all the shaders will have to be recompiled for new scalling that you set!
Therefore it is mandatory to be consistent with scalling that you set, if you use “Medium” scalling make sure all your new project use that scalling and make sure you don’t change it across projects because that will trigger shader recompiling a new.
btw. Scalling options are set under “Settings → Engine scalability settings” which is accessed from editor top right menu button called “Settings”
But there is a catch!, when you start a new project you must ensure not to select “Maximum” quality but rather “scalable” quality under “new project” dialog.
By checking “scalable” from dropdown menu your setting from previous project will be preserved and shaders won’t recompile, however if you leave “maximum” checkbox enabled (which is the default" then all shaders will get recompiled for “Epic” scalability if not already compiled.
Bottom line is that, set your desired scallability option (which depends on your GPU qulality) and make sure you don’t use “maximum” quality when creating new projects.
This will result is way much less of shaders being compiled because the engine will reuse already compiled shaders.
I hope this information helps you in stress free coding 
If you have additional questions regarding editor launch time and performance let me know because I have invested some time and strugling with these issues and my end result is that editor runs much faster and with less resources being consumed.
PS: To be able to change scalling options you must launch the editor, which will likely trigger shader compiling, but I have not yet figured out how to set scalling beforehand so don’t consider this to be a failure of the steps provided here, that’s how it is and is effective only for first run.