You're mixing "Copy the current selection" with "put a screen capture of the selected area on the Clipboard" -- I'm going to assume you mean the second.
There's a "Prompt for Screen Rectangle" Action that will pause until you select an area. The "Screen Capture" Action can capture an area of the screen to the System Clipboard, and you can set that area to be that selected with the previous "Prompt".
If that's not what you are after then work through your process manually, noting what you do at each step along with any assumptions you make and decisions you take, then post the list of steps here so people can see your desired workflow.
Another question within clipboard for another macro.
Trying to copy image within a websearch (my case duckduckgo images). I already set the macro but something weird is that the copied image I selected is not the one being pasted on pages but rather the previous one in the clipboard.
Edit to add: I see you've worked out why -- here's a more responsive solution that doesn't rely on a hard-coded pause.
It takes a beat for data to be copied -- the KM "Copy" Action waits for the System Clipboard to change before continuing, but if you are using the contextual menu "Copy Image" menu item you'll have to build that in yourself.
The System Clipboard has a "clipboard seed" property -- a number that changes every time the Clipboard does. So you save the original CLIPBOARDSEED() to a variable then test the current seed against the original -- when they are different the copy has happened and your macro can continue.
