On open lists, you are only able to edit items that you have created. This is why you may see the checkboxes disabled and greyed out next to some items.
You can update the details of multiple items in a list by using the Edit Multiple feature. To do this:
1. Go to the list of the items which you would like to update.
2. Tap the Item Actions button located on the left-hand side of the toolbar at the bottom of your screen.
3. Tap Edit items from the menu which pops up. Your items will now move over to the right and reveal their checkboxes.
4. Check the items which you would like to update and tap the ✓ which is now located in place of the Item Actions button on the left-hand side of the toolbar at the bottom of your screen.
5. You will now be presented with the Edit items screen.
6. Enter details which you would like to apply to all of the checked items. The checkboxes will automatically select when you enter the details.
7. When you are done make sure the checkboxes are checked for the fields to which you would like to apply the updates and tap the ✓ in the top right of your screen. All of the items which you selected in step 4 will now be updated with this new information.
Note: You can also use this feature to remove information from all of the items in your feed. To do so, leave the field blank but check the checkbox next to it. When you tap ✓ this field will now be made blank for all of the items which you selected in step 4.