when I am connecting mist to a private network I don't have the mining option neither. However, when I start mining from the geth javascript console, mist does indicate that my node is currently mining

here is how I set things up (given that setting up a private network is still not straightforward in my opinion).
create a workspace:
$ mkdir devnet
$ cd devnet
devnet$ mkdir node1
create account for your mining node
devnet$ geth --datadir node1/ account new
save your address and password. Append 0x to your address. Create a genesis file with puppeth (or just google for a simple genesis file)
devnet$ puppeth
now initialize your node
devnet$ geth --datadir node1/ init genesis.json
start your node. Use same networkId as defined in genesis file (using puppeth)
devnet$ geth --datadir node1/ --port 30303 --rpc --rpcport 8545 --rpcapi "personal,db,eth,net,web3" --networkid XXX
see geth Command line options for all commands.
connect a web3 javascript console to your geth node
devnet$ geth attach ipc:node1/geth.ipc
(or ~$ geth attach "http://localhost:8545")
> personal.unlockAccount(eth.coinbase, 'password', 0)
> miner.start()
> exit // to quit the javascript console
or everything in one signle command
devnet$ geth --datadir node1/ --port 30303 --rpc --rpcport 8545 --rpcapi "personal,db,eth,net,web3" --networkid XXX --unlock '0xaddress' --password passwords.txt --mine
connect mist to your node
devnet$ mist --rpc node1/geth.ipc
(or ~$ mist --rpc "http://localhost:8545")
here is the file structure for clarity:
devnet$ tree -L 2
.
├── genesis.json
├── node1
│ ├── geth
│ └── keystore
└── password.txt
ReferenceError: 'miner' is not definedI have checked, my file structure is the same as yours except forgeth.ipcin the node1 folder. I also could find a networkID in the genisis file so I used0as it is the first network I created. – Chris Feb 03 '18 at 06:31networkId=1then you're on the mainnet and mining real ether (but in that case you don't need a genesis file as those values are predefined in geth source code). you can do it ! :)