If I have multiple photos selected at the bottom row and press P, only the highlighted photo of the selection is flagged, not the whole selection.
In develop module, how do I flag multiple photos at the bottom?
Press in this order;
D on the keyboard.
In the Library Module:
I have two images selected:
You can always right click after selecting the photos and flagging them that way. I don't know of a shortcut unfortunately.
So on the bottom left you have several different viewing options (right above that bottom row where all your photos are flagged). There's one with the number 1 in a box, one with the number 2 in a box, and then one with 4 boxes next to each other (and then arrows and other symbols if you keep going to the right). Click the symbol with the four boxes. This should bring the photos you've selected into the library filter and show them all in the viewer (whereas usually you'd just see one photo there). Make sure you've selected in the bottom row all of the photos you want to delete and then with them there in the viewer you can hit "x" and it'll flag them all as rejected. Then you can right click on the photos and you'll see the option to "remove photos." This should do it for ya.
Develop mode - focus shifts to the main photo displayed, but the filmstrip still shows the selected photos. Solution? Right click on the filmstrip at the bottom -> Pick flag
The other option is of course, Library Mode (shortcut key G like it was said here) and then Develop mode again after flaggin (shortcut key D)
Lightroom has been developed with a particular workflow in mind: It starts in 'Library' mode, where you are to review, cull and rate your images. Next, you move to the Develop module, where you Develop individual images. After this, you then can move into other post-processing tasks, such as Web, Print, etc.
This means that the Library Module is designed for rating images, and allows you to select multiple images and 'pick' or flag them. Develop module is designed for single images, so it is no surprise that selecting multiple in the contact sheet sheet doesn't work.
Use the Library Module.