After the declaration of 'odds' any other text after it is invalid e.g.

Ss^0.5 or s
Tt^0.5 || t

If you want a randomized value for that in which Tt has odds of 0.5 to being chosen you could have:

{Ss^0.5|s}

{Tt^0.5|t}

If you want to add 'odds' with HTML formatting, you should place the odds after the items e.g.

<u>Ag^0.5</u>

to

<u>Ag</u> ^0.5

The change in odds should always be on the end of the item.

On your [m = markings6.selectUnique(1,7).joinItems("/")] you are setting the value of m to be the joined items in a string, not the list. To fix it you just need to store it on the variable, then use the joinItems on the variable after: [m = markings6.selectUnique(1,7), m.joinItems("/")]

Then to output the names: [m.selectAll.map(a => a.name).joinItems("/")] in which it would iterate on the markings on m and get their name, then joinItems them.