I want to be able to click on bathroom fixtures and collapsible list appears with toilet roll holders, towel rings, soap dishes, shelves, hooks, mirrors & cabinets etc (with a little dropdown arrow)
All depends on what you want to do, you can do simple with just having a collapsed container or box that all the list items are attached to.
This container or box needs to be set as collapsed on load and then when uses click on the bathroom fixtures text element or button or simple arrow icon, then the onClick event handler is setup to make the collapsed container or box expand.
You can simply add another button or arrow icon with the same process, however setting the container or box to collapse again.
https://www.wix.com/corvid/reference/$w.CollapsedMixin.html
Just note that you need to remember that whatever you have set on your page to collapse, that when it expands the container or box will push everything underneath it down the page to accommodate the container or box being expanded on your page.
https://support.wix.com/en/article/corvid-how-page-layout-is-affected-when-elements-change-size
Otherwise you can be more clever or technical and do something like in these tutorials here.
https://codequeen.wixsite.com/double-collapse/double-collapse-code
https://www.youtube.com/watch?v=HmTkf5af0NE - youtube video of above tutorial
https://www.wix.com/corvid/example/collapse-elements - Wix tutorial that you can open in your editor with all code and elements already setup.
thank you so much for responding. I only need it to show or collapse a list on the bottom two bullet point
So just simply have an arrow icon at the end of each line that the user can click on to expand the collapsed container or box on both of them.