Upload Bandwidth can be limited in the Time Shift Sync feature for each Share.  Administrators can specify a schedule the bandwidth allocated during those time frames. The default value for each time slot is FULL.

Alternatively you can set up traffic limit(s) on your Router or Switch to control upload bandwidth. Based on the model and make of your Router or Switch, you can set up the bandwidth from its management UI. For example, a low cost smart switch (TP-LINK Easy Smart Switch, $40 street price ) will allow you to set up traffic bandwidth limits.