[chaley]

Originally Posted by foosion

I have thought they have something to do with ondevice because they appear in a column with the lookup name "ondevice".

They appear in the line number column, not the ondevice column.

I had thought Reading List, when I plug in my device, checks what books are on the device and marks the ondevice column for books that are on the device.

Calibre populates the ondevice column, not reading list. It appears even if reading list isn't installed.

When I click View List from Reading List, it searches for those marks (using the search bar function), so that only books with that mark are visible and it makes the ondevice column visible as the leftmost column.

That means you have asked reading list to make a list of books currently on the device. The list is updated when you connect.

When you select the list, reading list sets the mark for each book in the list then searches for that mark. The ondevice column isn't used for this.

When I clear the search bar, it lists all books and the ondevice column continues to be visible.

Only if the device is still connected.

Marks will continue to show in the line number column.

When I restart Calibre, the ondevice column is no longer visible (since it's in a position to the right of visible columns).

I think you are talking about marks. They exists only for the current calibre session. Restarting calibre clears all the marks.

I'd rather the column was only visible when I want it to be visible and that there was an easy way to make it not visible other than restarting Calibre.

Apologies if I'm being obtuse.

Simply clear all marks with the Mark Books action.

What I think you are doing is using Reading List to keep a persistent record of what was on the device the last time you connected. When the device isn't connected then you are then selecting that list to see the books. Because reading list uses marks to do its job, you see the mark pins. There is no ondevice column. When you are done, clear the marks.

You can avoid using marks by having reading list update a custom column or the tags column when you connect. For example, reading list could add/remove the tag "OnDevice" when you connect the device. This will persist after you remove the device. You then use search to find books with or without the tag OnDevice, as you wish.