Customize shortcut delay when opening Preferences on the Icons page

The customize shortcut (mini-toolbar) appears more slowly when opening Preferences to the Icons page compared to other pages.

Do you have lots of icon sets installed, or an icon set with lots of images in it?

I have 22 icon sets installed, with nearly 16k icons in total. The last four sets are SVGs.

# Icon Set No of Icons
1 Internal Icon Set 306
2 Directory Opus 9 248
3 FLUENT.dis 369
4 FLUENT_UI_APRICOT.dis 394
5 FLUENT_UI_BLUEBERRY.dis 394
6 FLUENT_UI_DUALTONE.dis 397
7 FLUENT_UI_MINT.dis 394
8 FLUENT_UI_MONOTONE.dis 397
9 FLUENT_UI_PLUM.dis 394
10 FLUENT_UI_RASPBERRY.dis 394
11 FLUENT_UI26_THIN_APRICOT.dis 394
12 FLUENT_UI26_THIN_BLUEBERRY.dis 394
13 FLUENT_UI26_THIN_DUALTONE.dis 397
14 FLUENT_UI26_THIN_MINT.dis 394
15 FLUENT_UI26_THIN_MONOTONE.dis 397
16 FLUENT_UI26_THIN_PLUM.dis 394
17 FLUENT_UI26_THIN_RASPBERRY.dis 394
18 IconSet Himmelsbla v1.2 Dual.dis 630
19 feather.dis 287
20 ms_icons.dis 2,422
21 tabler_io_filled.dis 1,053
22 tabler_io_outline.dis 5,093
Total 15,936

Remove any you don't use (and maybe avoid or split up ones with thousands of icons you don't use) and it should process them a lot faster.