Truly delete all Apex logs in your org.

DeleteApexLogs.js

var loadScript = (src)=>{
    return new Promise( (resolve, reject)=>{
        var script = document.createElement('script');
        script.type = 'text/javascript';
        script.src = src;
        script.onload = resolve;
        script.onerror = reject;
        document.head.appendChild(script);
    } );
}

var loadScripts = (urls)=>{
    return Promise.all(urls.map(url=>{return loadScript(url);}));
}

var queryRows = async (query)=>{
    return new Promise ((resolve,reject)=>{
        sforce.connection.query(query,{
            onSuccess: resolve,
            onFailure: reject,
        } );
    });
}
var queryMoreRows = async (queryLocator)=>{
    return new Promise((resolve, reject)=>{
        sforce.connection.queryMore(queryLocator, {
            onSuccess: resolve,
            onFailure: reject,
        });
    });
}

var queryLogs = async (query)=>{
    console.log(query);
    var logs= [];
    result = await queryRows(query);
    console.log(result);
    result.records.map(row=>logs.push({
            Id: row.Id
        }));
    while(result.queryLocator){
        result = await queryMoreRows(result.queryLocator);
        console.log(result);
        result.records.map(row=>logs.push({
            Id: row.Id
        }));
    }
    return logs;
}

var deleteLog = (id)=>{
    return axios.delete(`/services/data/v44.0/sobjects/ApexLog/${id}`,{
        headers: {'Authorization': 'Bearer ' + sforce.connection.sessionId},
    });
}

var chunk = (arr, count) => {
    var newArray = [];
    while (arr.length > 0) {
        newArray.push(arr.splice(0, count));
    }
    return newArray;
}

loadScripts([
'/soap/ajax/44.0/connection.js',
'https://unpkg.com/axios/dist/axios.min.js'
])
.then(()=>{
    sforce.connection.sessionId = window.getCookie('sid');

    console.log(sforce.connection.sessionId);

    var apexlogs = [];

    var query = `
        select Id from ApexLog
    `;

    (async (query)=>{
        var result = await queryLogs(query);
        console.log(result);
        var acc = 0 ;
        total = result.length;
        chunk(result,50).reduce((promise,chunk)=>{
            return promise.then(response=>{
                acc += chunk.length;
                console.log('deleted ', acc, '/', total, chunk);
                return Promise.all(chunk.map(row=>{
                    return deleteLog(row.Id);
                }));
            });
        },Promise.resolve());
    })(query);
});

登录后在任意SF页面将代码粘贴到 chrome console 里运行即可