How to use <iconID> in #showtooltip
 

I've been trying to find the appropriate way to assign #showtooltip macro icons through the use of icon ID/Icon name rather than a spell name or selecting a static icon.
A faint memory tells me it's possible but I've found any information on the subject surprisingly troublesome to come by...
This question didn't exists until I began creating utility macros enabling me to create addon binds otherwise unlisted in the "Game Menu > Keybindings" menu. The challenge in finding suitable icons; even with with "LargerMacroIconSelection" addon - made me want to take a closer look into using icon name/id...

The surprising lack of information made to decide to ask among the many capable users here on Wowinterface, in the hopes that you can enlighten me...

Is it possible? And if so, what's the syntax? Say you wanted to use this icon but are unable to find it using the ingame GUI, but you know the icon name or icon id?
https://wowwiki.fandom.com/wiki/File:Inv_gizmo_02.png

Name: Inv_gizmo_02

You have to manually select from the icon list if you want a specific icon. #showtooltip only shows a specific ability you have.

I know about icon selection, but doing so means loosing the dynamics of #show... For someone like me whom enjoys spending hours contemplating, building, and testing all kinds of macros, designing them with functionality in mind - surrendering the dynamic icon display just isn't an option...

It appears to be a problem with a relatively straight forward answer right? I never learned to speak "Google" which occasionally means that even "research" can become a headache. Knowing the relevant search terms/keywords I was very surprised that it would take me 3-5 hours to find a forum post dedicated to the use of ID's.
Upon reading the feedback I realized that either the question was misunderstood or I failed to properly explain myself initially...

So to respond to your reply Phantom; ID's are usable with #show and the syntax are as follows:
#showtooltip [spellname] ───BECOMES ──›› #showtooltip [item:43646]

@JahirahDK
This doesn't work.
That doesn't mean it didn't at one time, but it's not working now.

Late reply that the OP will probably never read and is not the solution they were looking for
but LargerMacroIconSelection can let you select icons by FileDataID, besides searching for icon name

@Ketho
Just wanted to thank you for your contribution on this topic... I've gotten a lot of help and great feedback from the Wowinterface users so I often swing by the forums often returning to this particular post as I'm still trying to find a yes/no answer to whether it's possible to combine the #show dynamics with specified iconIDs to allow for something like this:
When [mod] is used it will show the 'Spell' icon, otherwise it will show the icon of the designated iconID...

Don't think that's possible. #show (or #showtooltip?) only support spell names iirc