You can use the different search options in All or Messages to narrow down results.
- To search for chats from a specific user, select from: @user or to: @user.
- To search inside a channel or chat with a specific keyword, select in: #channel or chat.
- To search for chats based on specific time, select either after: a date, before: a date, or on: a date.
- To search for files and links, select either filenamehas: filename, linkhas: linkdetail, or filehas: filecontent.

Although, these options can be used individually, they can also be combined to show more accurate results.
Here are a few examples of how to use combined search:
- from: @user in: #channel before: a date
- from: @Rachael Matthew in: #zylker announcements before: 03/28/2022

- in: #channel before: a date filenamehas: filename
- in: #Emma Cartner before: 04/11/2022 filenamehas: *.png