It would be great if Customize Toolbar would permit adding any function that is available in the menus. In my case, I wanted a button to open the Windows Character Map.
The ability to put a shell command in a toolbar button would also be powerful.
Thank you for a fantastic piece of software! I’m really enjoying myself.
We do not have nearly the budget to create the hundreds of icons that would be required to make that possible, to the standards of quality we are comfortable with. We critique each icon individually and sometimes go over several revisions with the designer, that may seem excessive but that is just how we do. 
This is especially true considering that going forward, we have to design two entirely different sets of icons for low and high-res monitors.
Artisan icons! Hand-crafted! Brewed with love, polished by unicorn hair!
Just another service brought to you by L&L.
And never over-hopped!
Note: No unicorns were harmed in the making of this thread. The unicorn hair used to polish icons is collected daily from hand brushes after grooming. All unicorns are free-range, have a diet of fresh rainbow juice, and are allowed to age naturally. Literature and Latte has been independently validated as unicorn friendly. This message is a public announcement by the Save The Unicorn Foundation of Southern Gondwana.
Why doesn’t that surprise me 
tch! tch!
Move over Blade Runner.
How does the alternative work? Warped space-time?
I’ve added a simple AutoHotKey toolbar overlay, for those who are comfortable augmenting their Scriv capabilities with AHK button bars and macros in a minimalist aesthetic.
Toolbar overlay, with “Character Map” and “Reveal in Binder”
Rgds – Jerome
Denying the capability on that basis was a poor call, in my view. Text buttons are a routine option in customized toolbars, as in Office prior to the Ribbon. I have “Reveal in Binder” and “Lock in Place” on a simulated toolbar via AutoHotKey, and deploy these buried commands much more freely as a result. With appreciation for Scrivener’s visual appeal, and for the need to focus on its most useful icons, I’d recall the miracle of the alphabet. We’re people of the word, not constrained to those tasks we can easily portray in hieroglyphs.
Hope you’ll reconsider – Jerome
It’s my personal opinion, but I think a mixture of text buttons and icons looks rather bad. I know that’s how Microsoft does it with their ribbon design, but everything about the ribbon makes me want to cry, from a design standpoint as well as usage. I have nothing against text buttons on a toolbar, to be clear, but only if that is the mode of operation: as in no icons at all, just text. I kind of like that look, and when I do find myself in a program that forces toolbars for normal usage, if it has the option for text only, I take it.
Technically not necessary, as explained via Fleinstein’s unicorn exception theorem. Unfortunately it’s difficult to validate empirically without placing unicorns in a particle accelerator and, to date, no university will give ethics approval. Despite this, I wouldn’t put it past unscrupulous unicorn farmers to warp space time to increase profits.
youtube.com/watch?v=_EPsuOEH1fY Awww bless! 
And how does unicorn differ from other species or breeds of corn? 
(I must admit being somewhat at loss about how corn is connected to custom iced toolbars being more flexible…). 
{… and a toolbar is where you get tools, and possibly a drink?} 
It’s uniquecorn
and:
The sense of humour, of those tooled-up, alcohol enhanced customers, usually tends t’wards being ‘corny’,
merriam-webster.com/thesaurus/corny and their appreciation of all thing pertaining to propriety is at best elastic.
“Aaahhh… Now I get it” he said, and bent the customized toolbar so it’d fit in the corn’er.
Well, you do appear to be getting the picture. [size=50]not before time[/size]