If there are four different parts I am wanting on Bricklink, is there an easy way to see if one shop has all four? I would want to get it from one shop to reduce shipping. I know I could do it the long way, but if I don't find one early it could take a while.
The way to do it is to make a wanted list in BrickLink, selecting all the different pieces and quantity of each that you want.
Then select all of the items by checking the boxes next the items you want or selecting the upper box to select them all and then click the green buy items button, this then brings up a list of stores selling the items. The list is sorted by which store has the most of your selected items available to sell. The two important columns on this list under each store is "unique lots" which is how many of your different parts the store has followed by "item count" which is the quantity of those items they have.
If you then click on the individual store, their shop will have a wanted list tab, which will show you everything on your wanted list that they have to sell.
It's not uncommon to have to purchase from multiple shops to get everything (different items and quantity) you need/want. So it often requires checking multiple stores to combine it into the smallest number of purchases, I am not aware of any automated method of doing this, I just end up opening multiple tabs in my browser from the list of stores generated by my wanted list query and figure out the best option myself from there.