1. Results saved in the first search are not added to a second search, it always resets. Example if I search for a sku landmark, and I search for another sku, I'll mark it should be 2 sku will be only the last one. This is true for all Magento grids. The main grids are: Orders, Products, products from categories.
2. In the product grid we need to search several skus at once, create a way to put a sku list and run the search.
3. In the product grid we need to search by category, one or several categories at once.