user109777: I couldn't find any documentation on this.
I found that the options for fee_method are eta, static and mempool by reading the source code. But it's still not clear to me how fee_level relates to the fee_method, does it have something to do with configuration? If that's the case, the configuration isn't documented either. What is to be set? How does it work?

user-1: There are 3 options(fee estimation methods) available for fee_method: static, eta and mempool
static - static fees
eta - based on confirmation within N blocks
mempool - based on mempool depth

fee_level for ETA can be one of these values in Electrum GUI: 25,10,5,2
FEE_ETA_TARGETS = [25, 10, 5, 2]
https://github.com/spesmilo/electrum/blob/ea22d0073ea5f61d53449a7afd072c3fd78003e8/electrum/simple_config.py#L23

fee_level for Mempool can have one of the value mentioned below in Electrum GUI:
FEE_DEPTH_TARGETS = [10000000, 5000000, 2000000, 1000000, 500000, 200000, 100000]
https://github.com/spesmilo/electrum/blob/ea22d0073ea5f61d53449a7afd072c3fd78003e8/electrum/simple_config.py#L24


109777: <p>I couldn't find any documentation on this.</p>
<p>I found that the options for fee_method are <code>eta</code>, <code>static</code> and <code>mempool</code> by reading the source code. But it's still not clear to me how <code>fee_level</code> relates to the <code>fee_method</code>, does it have something to do with configuration? If that's the case, the configuration isn't documented either. What is to be set? How does it work?</p>
 -1: <p>There are 3 options(fee estimation methods) available for <code>fee_method</code>: <code>static</code>, <code>eta</code> and <code>mempool</code></p>
<p><code>static</code> - static fees</p>
<p><code>eta</code> - based on confirmation within N blocks</p>
<p><code>mempool</code> - based on mempool depth</p>
<p><a href="https://i.stack.imgur.com/8gawN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8gawN.png" alt="electrum-fee-2" /></a></p>
<p><code>fee_level</code> for ETA can be one of these values in Electrum GUI: 25,10,5,2</p>
<pre><code>FEE_ETA_TARGETS = [25, 10, 5, 2]</pre></code>
<p><a href="https://github.com/spesmilo/electrum/blob/ea22d0073ea5f61d53449a7afd072c3fd78003e8/electrum/simple_config.py#L23" rel="nofollow noreferrer">https://github.com/spesmilo/electrum/blob/ea22d0073ea5f61d53449a7afd072c3fd78003e8/electrum/simple_config.py#L23</a></p>
<p><a href="https://i.stack.imgur.com/fxrEf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fxrEf.png" alt="electrum-fee-1" /></a></p>
<p><code>fee_level</code> for Mempool can have one of the value mentioned below in Electrum GUI:</p>
<pre><code>FEE_DEPTH_TARGETS = [10000000, 5000000, 2000000, 1000000, 500000, 200000, 100000]</pre></code>
<p><a href="https://github.com/spesmilo/electrum/blob/ea22d0073ea5f61d53449a7afd072c3fd78003e8/electrum/simple_config.py#L24" rel="nofollow noreferrer">https://github.com/spesmilo/electrum/blob/ea22d0073ea5f61d53449a7afd072c3fd78003e8/electrum/simple_config.py#L24</a></p>
<p><a href="https://i.stack.imgur.com/37CHu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/37CHu.png" alt="electrum-fee-mempool" /></a></p>
