{
    "alt-speed-down": 50, 
    "alt-speed-enabled": false, 
    "alt-speed-time-begin": 540, 
    "alt-speed-time-day": 127, 
    "alt-speed-time-enabled": false, 
    "alt-speed-time-end": 1020, 
    "alt-speed-up": 50, 
    "bind-address-ipv4": "0.0.0.0", 
    "bind-address-ipv6": "::", 
    "blocklist-enabled": false, 
    "blocklist-updates-enabled": true, 
    "blocklist-url": "http://www.example.com/blocklist", 
    "cache-size-mb": 4, 
    "compact-view": false, 
    "dht-enabled": true, 
    "download-dir": "/home/inherit/Загрузки", 
    "download-queue-enabled": true, 
    "download-queue-size": 5, 
    "encryption": 1, 
    "idle-seeding-limit": 30, 
    "idle-seeding-limit-enabled": false, 
    "incomplete-dir": "/home/inherit/Загрузки", 
    "incomplete-dir-enabled": false, 
    "inhibit-desktop-hibernation": false, 
    "lpd-enabled": false, 
    "main-window-height": 500, 
    "main-window-is-maximized": 1, 
    "main-window-width": 645, 
    "main-window-x": 155, 
    "main-window-y": 127, 
    "message-level": 2, 
    "open-dialog-dir": "/home/inherit", 
    "peer-congestion-algorithm": "", 
    "peer-limit-global": 240, 
    "peer-limit-per-torrent": 60, 
    "peer-port": 51413, 
    "peer-port-random-high": 65535, 
    "peer-port-random-low": 49152, 
    "peer-port-random-on-start": false, 
    "peer-socket-tos": "default", 
    "pex-enabled": true, 
    "port-forwarding-enabled": true, 
    "preallocation": 1, 
    "prefetch-enabled": 1, 
    "queue-stalled-enabled": true, 
    "queue-stalled-minutes": 30, 
    "ratio-limit": 2, 
    "ratio-limit-enabled": false, 
    "recent-download-dir-1": "/media/inherit", 
    "rename-partial-files": true, 
    "rpc-authentication-required": false, 
    "rpc-bind-address": "0.0.0.0", 
    "rpc-enabled": false, 
    "rpc-password": "{2b4d4ed537bded2b75514ab6801c9cadabc800a1IDjAOX1O", 
    "rpc-port": 9091, 
    "rpc-url": "/transmission/", 
    "rpc-username": "", 
    "rpc-whitelist": "127.0.0.1", 
    "rpc-whitelist-enabled": true, 
    "scrape-paused-torrents-enabled": true, 
    "script-torrent-done-enabled": false, 
    "script-torrent-done-filename": "/home/inherit", 
    "seed-queue-enabled": false, 
    "seed-queue-size": 10, 
    "show-backup-trackers": false, 
    "show-extra-peer-details": false, 
    "show-filterbar": true, 
    "show-notification-area-icon": false, 
    "show-options-window": true, 
    "show-statusbar": true, 
    "show-toolbar": true, 
    "show-tracker-scrapes": false, 
    "sort-mode": "sort-by-name", 
    "sort-reversed": false, 
    "speed-limit-down": 100, 
    "speed-limit-down-enabled": false, 
    "speed-limit-up": 100, 
    "speed-limit-up-enabled": false, 
    "start-added-torrents": true, 
    "statusbar-stats": "total-ratio", 
    "torrent-added-notification-enabled": true, 
    "torrent-complete-notification-enabled": true, 
    "torrent-complete-sound-command": "canberra-gtk-play -i complete-download -d 'transmission torrent downloaded'", 
    "torrent-complete-sound-enabled": true, 
    "trash-can-enabled": true, 
    "trash-original-torrent-files": false, 
    "umask": 18, 
    "upload-slots-per-torrent": 14, 
    "user-has-given-informed-consent": true, 
    "utp-enabled": true, 
    "watch-dir": "/home/inherit/Загрузки", 
    "watch-dir-enabled": false
}

Transmission uses "system-wide" proxy settings, that is that they need to be set in such a way so that Transmission thinks they are used by the system in general.

Since Transmission uses libcurl then setting env-variables for Curl in the start-up script would probably be the easiest way.

https://forum.transmissionbt.com/viewtopic.php?f=2&t=14889&p=65228&hilit=HTTP+Proxy&sid=00f2d9dc09d40f4b7093b0bc57e0efb2#p65228