I ran:
./src/qt/bitcoin-qt -testnet -debug=NET

I got warning window. Anyway bitcoin-qt runs well. But How can I enable filter logging?
Here is the list.
namespace BCLog {
enum LogFlags : uint32_t {
NONE = 0,
NET = (1 << 0),
TOR = (1 << 1),
MEMPOOL = (1 << 2),
HTTP = (1 << 3),
BENCH = (1 << 4),
ZMQ = (1 << 5),
DB = (1 << 6),
RPC = (1 << 7),
ESTIMATEFEE = (1 << 8),
ADDRMAN = (1 << 9),
SELECTCOINS = (1 << 10),
REINDEX = (1 << 11),
CMPCTBLOCK = (1 << 12),
RAND = (1 << 13),
PRUNE = (1 << 14),
PROXY = (1 << 15),
MEMPOOLREJ = (1 << 16),
LIBEVENT = (1 << 17),
COINDB = (1 << 18),
QT = (1 << 19),
LEVELDB = (1 << 20),
ALL = ~(uint32_t)0,
};
}