This has always always ALWAYS irked me! I'm a build/buy CC creator so I enter/exit the game often to test things and 9 times outta 10 I only have "my" things I want to test in my mods folder because I'm using a "test" save on an empty lot with a shell box.
If you're not opposed to mods/cc ..... there are several mods that allow you to change the lights while in build mode.
thepancake1 & MizoreYukii have one (I have not tried this one yet.)
https://www.patreon.com/posts/edit-lights-in-1-50761483
And TwistedMexi has updated the Better Build/Buy mod to include this, which is the one I that I am using. With his you just shift/left click on the light and you get the exact same options as you do in live mode to adjust color/intensity.
https://www.patreon.com/posts/54871082
