the 1st thing I noticed when making a custom component is that whenever I paste into the IFrame Code popup it will scroll the window until the cursor/where I pasted is the last viewable line. Everytime I ctrl+v the window scrolls, it isn't a big deal if you're just pasting once but if you need to paste something on 2 consecutive lines you'll paste on the first line then the window scrolls so that line is the last viewable one so you have to scroll down to paste on the next line (horribly annoying unless you start from the bottom of the file and work your way upwards.
here, I have highlighted and copied the word 'options' on line 543 (note line 560 is at the bottom of the window):
and this is what it looks like after I paste over 'ret' on line 545 (you'll notice line 545 is now at the bottom of the window and all I did was press ctrl+v)
the other odd thing is in selecting the actual component.
clicking that blue tag with the components name (customComponent1 in this case) is the only way to select the component to make any changes. every other component you can click anywhere and it'll select it, but on custom components if you click to scroll, drag the scroll bar or even interact with literally anything rendered in it (buttons, text areas... any html element really) and it will not select the custom component.
small side note: I haven't noticed the bug where the code window magically moves the cursor to position 0 when working with the IFrame Code popup. I don't know if this was fixed, or if it's just a magic feature of custom components. in comparison to the magic cursor, these 2 problems I've had are fairly tolerable or just a minor nuisance.
edit: the magic cursor was not fixed, for whatever reason the IFrame Code window for custom components just doesn't have this bug.