Hello,

It really depends on exactly what parts of the UI you want to change. There are existing APIs and administrator features for specific parts of the UI.

For example, you can go to Admin->Folder->Project Settings->Men Bar to add custom UI to the menu bar that's in the header of each page.

If you want to add buttons to a data grid, you can specify this in XML metadata using the ButtonBarOptions part of the schema:

http://www.labkey.org/download/schema-docs/xml-schemas/schemas/tableInfo_xsd/complexTypes/ButtonBarOptions.html

You can set this XML on a particular table/query by going to Admin->Developer Links->Schema Browser, finding the schema and query you want to customize, clicking on Edit Metadata, and then on the Edit Source button. Example XML would look something like this:

        <tables xmlns="http://labkey.org/data/xml">
            <table tableName="Runs" tableDbType="TABLE">
                <buttonBarOptions position="both" includeStandardButtons="true">
                    <item text="Simple Assay Button" permission="READ" insertPosition="end">
                      <onClick>alert('button clicked');</onClick>
                    </item>
                </buttonBarOptions>
            </table>
        </tables>

Thanks,
Josh