Windows 10 brings its own share of limitations and inherent bugs like any other operating system, especially with the creation of system files and folders, following its installation. It takes an estimated 3-second wait time while Windows determines the type of folder template to be used based on its file content, before opening the folder you requested.
As Redmond Pie reports, you will often see the "Working on it..." message accompanied by a green progress bar in the address bar whenever there is a delay in opening the requested system folder. If you are affected with a similar issue, you could definitely get rid of it using an extremely simple fix as outlined below:
Step 1: Go to the affected folder and right-click on the empty space inside the folder window. Now choose 'Customise this folder' option via context menu.
Step 2: The Properties window of the chosen folder will now open up within the Customise tab.
Step 3: Under the Customise tab, locate the option titled "optimise this folder for:" with a drop down box next to it. Expand or open the drop-down box to reveal various options including General items, Documents, pictures, Music and videos.
Step 4: Choose the General items option and hit Apply or OK to save the changes.
That's it. You should now be able to open or launch any Windows system folders without the unexpected waiting time that you experienced earlier.
[Source: Redmond Pie]