What we still call a "palette" Apple more recently calls a "panel", and as with their older documentation with palettes, their first recommendation with panels is that we consider something else:
Consider alternatives to panels. Since panels take screen space away from content, many apps present auxiliary information and tools less intrusively using popovers, sidebars, split views, and toolbars. For example, Keynote, Numbers, and Pages include formatting panes that are attached as sidebars (which can be quickly hidden and revealed) to document windows.
https://developer.apple.com/design/huma ... ws/panels/
Of course when you truly need a palette you need a palette. But how often do we truly need a palette?
When we compare software made by xTalk users to professionally-published packages from major vendors, we find palettes used far less frequently among the pros. This is not a judgement of any particular use among our fellow community members; indeed, it would not be possible to express an opinion about any UI I've not seen. I offer that observation only in the spirit we all share, to reach inside ourselves for the best design solutions that reflect the best work we see in our industry.
Apple's note above is useful guidance. Always-on-top windows don't just obscure the Script Editor, they obscure everything. Where the functionality they provide is both immediate and frequently needed, they can be a good choice. But if not frequently accessed, the whole time they obscure the very windows we're working on with them. Compounding their inherent usability tradeoffs, palettes also have a notoriously small close box, so when you do decide to dismiss it that requires more care than for other window types.
Over the years as I became more aware of this trend to use palette alternatives among the software packages I use, I've considered and often used alternatives myself. One of the reasons I wrote my own Message Box is that I find it very useful to have open, but I want to be in control of when it's in front of what I'm working on, so I use a modeless style for that window.
Though palette is the default, LiveCode plugins can make use of all window styles. This can be set in LC's Plugins manager, creating a custom property that is persistent with the stack file so it can be reused and even shared and still retain the desired mode.
Please understand that none of this is in any suggesting palettes should never be used, or even that they shouldn't be used in the case being described here. I've not seen the plugin in question here, nor have any idea of the functionality it delivers, so AFAIK a palette mode may be ideal for it.
I offer this only as a general reminder of what Apple's and others' usability testing has shown us: palettes are great when you need them, but windows come in many styles, each has its own strengths and weaknesses, and all are supported by LC's Plugins subsystem.